I.U.D.'s used for the purpose of contraception are old in art, having been popularized by the development of Dr. Ernst Grafenberg's silver ring. Since that time, almost 40 years ago, there have been many improvements in both the configuration and the material of the device as well as the efficiency and the public acceptance of the device. The configuration of the I.U.D.'s most frequently used today may be categorized generally as coils, loops, rings and bows, the best known examples being those devices developed by Margulies, Lippes, Ota and Birnberg, respectively.
It has long been recognized that even though I.U.D's are safe, reliable and efficient, there are still several very important structural aspects that can be improved. For example, the I.U.D. must be capable of insertion using a thin-walled cannula and a push rod without the need for dilation of the cervix, such as described in U.S. Pat. No. 3,628,530 issued on Dec. 21, 1971 to Jerome Schwartz.
It has also been recognized that although the I.U.D. must be readily removable, if possible without surgical interference, yet it must be capable of resisting expulsion caused by the involuntary uterine contractions exhibited by the fundus muscle. These are, of course, diametrically opposite conditions, but which must nevertheless be met for the I.U.D. to be effective.
It has also been recognized that the I.U.D. for proper reliability must have a maximum contact with the walls of the uterus, which belief lead to the inflatable types closely conforming to the shape of the uterus, such as described in U.S. Pat. No. 3,452,749 issued July 1, 1969 to Edwin H. Riedell.
In U.S. Pat. No. 3,464,409 issued on Sept. 2, 1969 to James Murphy an I.U.D. is described which is inflatable through a tube after it has been inserted into the uterus and expands into a balloon-like configuration having pouch-like expansions around the periphery of the main balloon.
In U.S. Pat. No. 3,401,689 issued on Sept. 17, 1968 to Eugene C. Greenwood, a smooth-walled toroidal-shaped I.U.D. is described which is introduced into the uterus in a deflated condition and becomes inflated through a syringe.
In U.S. Pat. No. 3,782,376 issued on Jan. 1, 1974 to Irwin S. Lerner, an I.U.D. is described which is provided with spurs directed toward the cervix to prevent expulsion of the I.U.D.
It has not been, however, recognized that contact with the inner walls of the uterus is desirable rather at a plurality of smaller regions than at large surfaces in order to minimize irritations of the inner wall of the uterus and to avoid blockage of the menstrual flow. At the same time an I.U.D. answering the above requirements must have retained the last mentioned beneficial properties even under the expulsionary effects of the fundus and in addition assume a shape which laterally increases its size with respect to the cervix under the last-mentioned conditions and reliably prevents thereby its expulsion.